Stopping flicker during updates

When making major changes to a list control (and other controls) it is a good idea to turn off updating of the control. To do this you would use SetRedraw(false) at the start of the change and SetRedraw(true) at the end, and then invalidate the control.

However, SetRedraw simply turns redraw on or off, it does not let you know whether or not redraw was on or off before the call. And there is no function that can tell you this.

For this reason, I have my own SetRedraw function that counts the number of times you have turned it on and turned it off.

Define a member variable:
     int m_redrawcount;

In your contructor do:

     m_redrawcount = 0;

And then define the following function (in this case for a list control):

void CMyListCtrl::SetRedraw( BOOL bRedraw) {
     if (! bRedraw) {
          if (m_redrawcount++ <= 0) {
               CListCtrl::SetRedraw(false);
          }
     } else {
          if (--m_redrawcount <= 0) {
               CListCtrl::SetRedraw(true);
               m_redrawcount = 0;
               Invalidate();
          }
     }
}

The first time you turn redraw off, the real SetRedraw function is called to turn redrawing off. Subsequently the function increases a counter when you requested redraw be turned off, and decreases it when you request redraw to be turned on again. When the counter gets back down to zero, the real SetRedraw function is called to turn redrawing back on again and the control is invalidated (so that redrawing actually takes place).

This means you can not put SetRedraw(false) at the start of, and SetRedraw(true) and the end of, any function that makes large changes to the lsit control (like loading, sorting, changing with column widths or order etc).



Comments

Leave a Comment
  • Your email address will not be published. All fields are required.

Top White Papers and Webcasts

  • Live Event Date: October 29, 2014 @ 11:00 a.m. ET / 8:00 a.m. PT Are you interested in building a cognitive application using the power of IBM Watson? Need a platform that provides speed and ease for rapidly deploying this application? Join Chris Madison, Watson Solution Architect, as he walks through the process of building a Watson powered application on IBM Bluemix. Chris will talk about the new Watson Services just released on IBM bluemix, but more importantly he will do a step by step cognitive …

  • Businesses are moving more and more of their customer transactions to the web. Security is understandably a top concern as online transactions increase, so it is important to make sure your electronic signature provider meets the highest security standards. That means more than simply passing a security audit or obtaining a certification. This white paper provides recommendations for taking a broader view of e-signature security, and answers key questions that help identify the security requirements against …

Most Popular Programming Stories

More for Developers

Latest Developer Headlines

RSS Feeds